The invention relates to a support for holding and/or forming a dental prosthesis with an axis, an anchoring part for anchoring in a bone of the lower or upper jaw of a patient and/or in a master model and a head part intended to project from the bone and/or master model. This head part serves to support an originally separate element attachable to the support with a cap. The cap can for example be a part of a dental prosthesis such as an individual artificial tooth or a bridge or a prosthesis having several teeth. The possibility also exists however of first attaching a so-called burnout cap made of plastic to the support. The burnout cap can serve for making a casting model and a casting impression, then be burned off from the latter and replaced by a impression cap when the cast impression is used.
For certain applications, it should be possible to attach the cap in a specific rotational position on the support. A support known from EP 0 685 208 A has an implant and a secondary part having an external thread screwed into the internal thread of the implant and a head projecting from the implant. This forms the head part of the support and has an octagonal section as well as a conical section that tapers away from the latter to the front side of the head. A superstructure element or impression element with a cap can be associated with the known secondary part and have an internal space with an octagonal section. FIG. 1 of the present patent application is a cross section through an area of the octagonal section of the head of a known secondary part 1. The secondary part defines an axis 5 and straight lines running radially thereto through the corners of the octagonal head section, one of which is designated 7. Cap 10 is shown in FIG. 1 in the central intended rotational position provided. In this position, each corner of the octagonal section of the internal space of the cap is on the straight line 7 running through the associated corner of secondary part 1. The cap rests on the secondary part with radial play so that the mutually associated octagonal surfaces of the secondary part and the cap are at a distance a from each other. The radial play must be so great, particularly when burnout caps are used, that the internal weight of the superstructure element then made by casting can differ due to shrinking processes and the like from the internal weight of the burnout cap. Because of the play, cap 10 can be turned starting in its central desired rotational position in two rotational directions through an angle designated a in FIG. 2 until the octagonal surfaces of the cap are located at the corners of the secondary part. Distance a is typically approximately 0.02 mm and possibly even more with burnout plastic caps. Angle a then amounts to approximately 2.25xc2x0 or more. The cap can be rotated back and forth through an angle 2a, namely approximately 4.50xc2x0 or more. The octagonal head section of the known support thus makes possible only very inexact positioning of the cap relative to rotations about the axis. If large forces act on the cap approximately perpendicularly to the axis and bring about shear forces or torsional forces between the cap and the support, there is the danger that the cap will execute small rotational or swiveling movements relative to the support. Such tiny rotational movements may cause the dental treatment to fail. The cap can be mounted on the head in one of eight selectable rotational positions. Sometimes, however, it is advantageous for the cap to be placed on the support in only a single rotational position, which is not possible with the known support. Moreover, the cap rests only on the octagonal section, but not on the conical section of the head. In this known head, it would also be practically impossible to design a cap so that it abuts both the flat surfaces of the octagonal section and the conical section of the head. Since the octagonal section has only a relatively small axial dimension, the cap receives little support with respect to laterally acting forces, i.e. forces transverse to the axis, impairing the stability of the connection of the cap or the superstructure element to the additional support.
DE 195 34 979 C discloses a support with an implant and a spacing sleeve. The latter serves as a head for attaching a dental prosthesis. The implant has an axial blind hole. Its internal surface is provided with six grooves distributed around the axis of the implant. The spacing sleeve projects into the blind hole of the implant and has noses engaging these grooves so that the spacing sleeve can be positioned in six different rotational positions in the implant. This support has the disadvantage however that the spacing sleeve is guided laterally only in a short cylindrical guide area of the hole having a relatively small diameter below the grooves and is supported against the forces directed approximately transversely at the implant axis. If such forces act on the dental prosthesis, a long lever arm is produced between the point where these forces act and the guide area of the hole, so that very high torques have to be transmitted from the spacing sleeve to the implant in the guide area of the blind hole. In combination with the small dimensions of the guide area, this results in a high risk of the dental prosthesis executing micromovements relative to the implant when stressed, leading to failure of the dental treatment. Moreover, the implant of this known support must be inserted approximately flush with the ridge of the bone. This subgingival arrangement of the implant has the disadvantage that the gum (gingiva) knits over the implant during the healing phase and requires a further incision to attach the spacing sleeve. Moreover, the dental prosthesis cannot be removably fastened to the spacing sleeve. Moreover, the known support is not suitable for anchoring bridges, either.
A support shown in FIGS. 1-3 of CA 1,313,597 A has an implant and a generally conical sleeve. There are two axial projections at the upper end of the implant which, when the device is assembled, engage flats on the sleeve and position it non-rotatably in one of two possible rotational positions. In the version shown in FIGS. 4 and 6, the implant has a projection that is generally cylindrical but is provided on one side with a flat. The flat permits non-rotatable positioning of the sleeve in a single rotational position. Since the two projections and the flat of these known implants each have only one flat surface tangential to the axis of the implant that abut a flat matching surface on the sleeve, these implants define the rotational position of the sleeve in the same way no more exactly than the supports commented on above and known from EP 0 685 208 A. In addition, these implants can position a sleeve in only two different rotational positions or even in only one single rotational position. In many applications, the rotational position of a cap, however, must be selectable from more than two rotational positions. In addition, the crown prosthesis in these implants must clearly be supported at least essentially by one additional cap whose rotational position is not defined at all. The supports known from CA 1,313,597 A that serve to hold a screw-on cap are also composed of at least three separate parts. This large number of parts makes dental treatment complicated and adversely affects the stability of the dental prosthesis in the mouth of a patient.
A support shown in FIGS. 1-3 of CA 1,313,597 A contains an implant and a generally conical sleeve. The implant has two axially projecting projections at the upper end which engage flats on the sleeve when the device is assembled and position them non-rotatably in one of two possible rotational positions. In the version shown in FIGS. 5 and 6, the implant has an extension which is generally cylindrical but provided on one side with a flat. The flat permits non-rotational positioning of the sleeve in a single rotational position. Since the two projections and the flat of these known implants each abut the flat opposite surface of the sleeve with only one flat surface tangential to the axis of the implant, just like the supports commented on above and known from EP 0 685 208 A, these implants define the rotational position of the sleeve only imprecisely. In addition, these implants can position the sleeve only in two different rotational positions or even in only a single rotational position. In many applications, however, the rotational position of a cap must be selectable from more than two rotational positions. In addition, the artificial crown in these implants is clearly supported at least essentially by an additional cap whose rotational position is not even defined. The supports known from CA 1,313,597 A that serve to hold a cap that can be screwed on are also composed of at least three separate parts. This large number of parts makes dental treatment complicated and adversely affects the stability of the dental prosthesis in the mouth of a patient.
EP 0 475 299 A teaches an implant or a basic body, a spacing sleeve upper part, and a spacing sleeve bottom part that can be screwed into the basic body. The basic body has an axial blind hole with female snap connectors distributed along its circumference into which the male snap connectors of the spacing sleeve upper part engage when the implant is assembled. The spacing sleeve upper part is guided in the implant only by an annular recess in the blind hole and is supported against lateral forces, in other words forces directly approximately transversely to the axis of the implant. Between the annular recess and the dental prosthesis, not visible, there is a relatively long lever arm. In addition, the annular recess is only relatively short and indeed must be short because the blind hole contains an internal thread and the female snap connectors as well. When forces act approximately transversely to the axis of the implant in the dental prosthesis, there is the danger that the spacing sleeve will make micromovements relative to the implant. In addition, additional separate parts in addition to the parts shown in EP 0 475 299 A are also probably necessary for fastening an artificial crown so that the entire device is composed of many individual parts, adversely affecting the stability even more.
The goal of the invention is to avoid the disadvantages of the known supports and of a device formed therefrom, as well as a superstructure and/or impression element and/or a healing element. In particular the opportunity is to be offered for an element with a cap to be normally positioned stably on the support in a rotational position defined as accurately as possible so that the cap, even with high forces acting on it approximately transversely to one axis of the support and/or torsional stresses, remains connected with the support permanently and in stable fashion. In addition, it should preferably be possible to secure a cap to a given support, depending on the design of the cap, in a rotational position selectable from one of several rotational positions or only in a single rotational position on the support. In addition, a device is to be created having a cap that can be fastened in stable fashion in any free rotational position to a support that permits the rotational position to be established.
This goal is achieved according to the invention by a support for holding and/or forming a dental prosthesis with an axis, and anchoring part intended for anchoring in a bone and/or a master model, and a head part intended to project out of the bone and/or master model and an annular shoulder surface located between the anchoring part and the head part and forming an angle with the axis; the head part has a peripheral surface as well as a face and the support is characterized by the fact that the head part has several projections and interstices located at the periphery and/or face and alternating around the axis.
The invention also relates to a device with a support and with an element that can be fastened to the support, with the device being characterized by the fact that the element has a supporting surface intended to rest on the shoulder surface and surrounds the head part in cross section in the state in which it rests on the shoulder surface.
Advantageous improvements on the support and the device follow from the dependent claims.
For example, the support can consist of a metal implant or primary part and an originally separate metal secondary part, preferably removably fastened to the implant, for example screwed thereto, which is provided with the projections and interstices serving for positioning. However, the support can instead have a one-piece body which extends from the free end of the anchoring part up to the free end of the head part and forms these ends so that the support consists at least essentially completely of a one-piece implant made of metal for example. In addition, the support can be made as a manipulating support placed by a dental technician in a master model made of plaster for example and is used to form a superstructure. The head part projecting out of the master model of such a manipulating support should then have the same design as a support used for insertion into a bone of a patient while the anchoring part of the manipulating support inserted into the master model usually differs from the anchoring part of the support placed in a bone.
The head part of the support according to the invention has interstices distributed around the axis. These interstices form positioning surfaces that are not rotational symmetrical with the axis for non-rotational positioning of a superstructure and/or impression element. Each interstice preferably forms a depression relative to a line that lies in a plane at right angles to the axis and contacts the head part on sides of the interstice facing away from one another. Each interstice for example is in the form of a groove or formed by a groove; the terms xe2x80x9cgroove-shaped intersticexe2x80x9d and xe2x80x9cgroovexe2x80x9d shall be construed to include both an elongate interstice and an elongate groove as well as an interstice or groove that has a width approximately the same size as the length or even greater than the length of the interstice or the groove. The interstices or grooves are open for example on the two ends that face away from each other. Each interstice is preferably delimited least partially by flats which are approximately parallel to a radial center line that runs through the axis and through the middle of the interstice or a central plane or form an angle of at most 60xc2x0 and preferably no more than 45xc2x0 with such a line or plane. Each interstice for example has two essentially flat, lateral surfaces and is approximately U-shaped or V-shaped in cross section. The interstices can however be at least partially or completely arcuate in cross section and for example can be at most or approximately semicircular. In this case then, for example at least certain flats of the arcuate limiting surface of each interstice can be located relative to a center line or center plane of the type mentioned above in the manner described above and/or define tangential planes arranged in the manner described.
An element, for example a superstructure element and/or an impression element and/or a healing element, can be fastened or possibly non-removably fastened on the support. Such an element can have a cap and/or be formed by a cap. The element can also have a burnout cap made of plastic or can consist exclusively of such a cap. The element or cap can rest on the annular shoulder surface of the support by a smooth, annular supporting surface surrounding the head part in axial projection, with no interruptions or gaps around the axis. The element can also have a least one projection which can engage an interstice of the head part of the support. The support can position such an element in at least one rotational position.
The projection, or each projection, engaging an interstice of the support of a superstructure element and/or impression element or other element and the projection (or each projection) of the support preferably engaging an interstice of the element can for example have a certain amount of play in the interstice so that the projection, despite possible inaccuracies in manufacture and despite changes in dimensions caused by changes in temperature, can be inserted easily into the interstice. The play measured along a circle surrounding the axis of the support or tangentially to such a circle can however be made so small that the superstructure element, in the state in which it has been positioned but not yet fastened, can be rotated back and forth through an angle that is preferably no more than 2xc2x0 and for example even only 1xc2x0 at most. This also is the case in particular in a burnable cap and a superstructure element cast and made with the aid of such a cap. The support therefore permits exact positioning of a superstructure element having at least one projection and/or impression element.
The head part of the support preferably has a section parallel to the axis and generally cylindrical and a generally conical section that tapers away from the latter toward the free end of the head part. The head part can then for example have groove-shaped interstices or grooves arranged on the peripheral surface and extending approximately axially, which extend at least through an area of the generally cylindrical section and through the conical section of the head part to the free end of the latter. The head part, instead of the interstices or grooves that are axial and arranged on the circumferential surface or in addition to such, can have interstices or grooves located on the face and running approximately radially, at least some of which have openings located in the circumferential surface of the conical section of the head part, or form such openings.
When an element is fastened to the support removably or non-removably and rests on the shoulder surface of the support, it can be supported by the head part at least at the conical section with at most a small amount of play with the conical peripheral surface and/orxe2x80x94when the head part has approximately axial interstices or grooves located at the peripheral surfacexe2x80x94in the interstices or grooves. The peripheral surface of the conical head section and/or the boundary surfaces of the interstices support the element in directions that run approximately at right angles to the conical circumferential surface and/or the axis of the support. When the interstices are located on the face of the head part and the element has projections that extend into such interstices, the lateral surfaces of the interstices support the element, among other things, also in directions that are at right angles approximately to the axis. The play between the conical peripheral surface of the conical section of the head part and the conical internal surface of an element fastened to the support can be made very limited. The play for example in the surface sections provided for support can be, for example in the radial direction and/or in directions that are at right angles to the conical surfaces, a maximum of 0.02 mm or only 0.01 mm at most and especially at the conical surfaces the play is preferably in the micron range, for example a maximum of 5 microns or 3 microns at most.
The axial dimension or height of the head part is advantageously so small that the implant can be placed optionally subgingivally or transgingivally or in a position in which it is semi-submerged in the gingiva in the mouth of a patient. The design of the head part makes it possible for the latter to support a superstructure element or impression element held by the support, despite a small axial dimension of the head part, in all directions running approximately transversely to the axis in all applications. This in turn ensures that the superstructure element fastened to least one support in the mouth of a patient will be connected stably and permanently with the support (or each support) serving to fasten it and will not be loosened even by high forces directed approximately transversely to the axis of the support or to the axes of the supports.
A superstructure or other element can therefore be fastened very stably, at least approximately free of micromovements, and permanently on the support relative to approximately axial forces, with respect to forces directed approximately transversely to the axis, and with respect to torsional rotation about the axis.
In a preferred embodiment, the interstices of the support include a plurality of first interstices with identical shapes and identical dimensions, especially identical widths and identical depths, and a second interstice which has a larger dimension in at least one direction than the first interstices and for example is wider and/or deeper than they. The first interstices adjacent to one another are equally spaced apart from one another as measured along a partial circle coaxial with the axis of the support and together define a division of a circle or simply a division. For clarification, it should be pointed out that the division is equal to the n-th part of a full circle where n is a whole number and is advantageously at least 6 and at most 72 so that the division angle is advantageously in the range from 60xc2x0 to 5xc2x0. In one advantageous embodiment, n is at least 8 and especially when the interstices are arranged on a peripheral surface, it is still more preferably at least 10xc2x0 and for example 12xc2x0 to 36xc2x0. The second interstice for example can be formed by the fact that, at least theoretically, one can start with identical projections and first interstices distributed uniformly on a full circle and remove or omit at least one and possibly more of these projections. The resultant second, wider interstice has a dimension measured along the partial circle which is equal to the sum of a dimension measured along the partial circle of a first interstice and one complete division or several complete divisions. A second, wider interstice can however be formed instead by making one projection or two adjacent projections narrower than the remaining projections.
An element fastened to the support for example can have a positioning section with projections distributed uniformly along its periphery which all have the same shapes and dimensions and are separated from one another by likewise similarly designed interstices and can engage all the interstices of the support. Such an element can be fastened relative to the axis of the support in various selectable positions, in other words rotational positions on the support, with each selectable position, i.e. rotational position, being defined by the mutually meshing projections and interstices of the superstructure element and/or impression element and/or the support and with the rotational angle between the adjacent rotational positions being equal to the divisional angle established by the division of the identically designed (first) interstices in the head part. This manner of connecting an element with the support is referred to below as multipositioning of the element.
The element can also have a projection that has a larger dimension in at least one direction than the first interstices of the support and is so designed that it can engage the second interstice but not the first interstices of the support. This projection for example can be wider than the first interstices of the support and/or have a height greater than the depth of the first interstices of the support. The positioning section of the element then for example has, in addition to this projection, projections that are even narrower and/or lower for engaging the narrower, first interstices of the support but possibly have only the projections that engage the second, wider and/or deeper interstice of the support. The element can then be connected relative to the axis of the support only at a single rotational position with the support. This manner of connecting an element with the support is referred to below as single positioning of the element.
However, the element can also be produced without a positioning section and especially without positioning projections and be made so that, after fastening to the support, it does not engage any interstices of the support. The element can then be rotated continuously when mounted on the support until it is fastened so that the element can be fastened for example at any rotational position. This is referred to below as free positioning of the element.
In one advantageous embodiment of the support, an element with multipositioning or an element with single positioning or an element with free positioning can be fastened freely to the support. The type of element that is best depends on its purpose, the type of dental prosthesis to be formed, and the individual medical symptom. If for example a crown for an individual tooth is to be produced as the superstructure element, preferably a superstructure element is used that permits multiple or possibly single positioning so that the crown is precisely positioned and protected against rotation. A prosthesis that replaces a plurality of teeth for example can be fastened by least two supports, each of which has a telescoping base that has a cap for single positioning. To form a soldered base, a cap can likewise be used for single positioning. A bridge or a rib structure for a prosthesis can be secured for example by caps for free positioning on supports. A laboratory that makes supports for example can make caps that fit on a support and are provided for various types of positioning, and for example on a set of identical supports, as needed, can supply the dentist with a set of identical caps or a set of caps for various types of positioning. The dentist can then use these caps as impression elements and/or for making different superstructure elements such as crowns, bridges, and prostheses, and/or healing elements. Therefore, a given type of support can be used to hold a plurality of different types of superstructure elements and impression elements.
Bridges, partial prostheses, and full prostheses are frequently fastened with two or possibly even more supports. In this case, the supports ideally have axes parallel to one another. However in practice the axes are frequently at an angle to each another and for example diverge or converge toward the free ends of the head parts. The device according to the invention is designed in one advantageous embodiment such that an element, for example an impression element or superstructure element, is mounted on the head part in a displacement direction inclined to the axis of a support and can be pulled off the latter. It is then possible to pull two or more elements held on supports away from the supports simultaneously if the axes of the supports are not parallel to one another and form angles with one another that measure up to 30xc2x0 or even up to 40xc2x0 for example. The element, when pulled away from the support and when connected with the latter, can be displaced in a direction over the head part which forms an angle of up to 15xc2x0 or even up to 20xc2x0 with the axis of each support.